What's in a Number?

John McCain will turn 72 in August. If elected, that would make him the oldest first-term president in history. Should that worry us? Not necessarily. To Dr. Michael Roizen, co-author of "You: The Owner's Manual," the more relevant information is the candidate's physical condition. After all, some 72-year-olds are fit for a marathon, while others are stuck in their easy chairs.

Roizen is the developer of the Real Age program, which uses an overall health evaluation to determine a person's true biological age (in contrast with his or her actual age). Using McCain's newly released medical records, Roizen walked NEWSWEEK through an assessment of McCain's physical status. Though some of the information Roizen normally requires was not immediately available—including specifics on McCain's diet and exercise habits and his resting pulse rate—the details at hand enabled him to make an initial assessment.

Starting from McCain's chronological age of 71.8, the Real Age program compared him with others of the same age on a variety of measures and added or subtracted years accordingly. And while McCain's own Mayo Clinic internist noted this week that "it is impossible to predict any person's future health," the results of the Real Age assessment should cheer the candidate.

Body Mass Index (weight in relation to height): With a weight of 163 and height of 5 feet, 9 inches, McCain's BMI works out to 24. The desirable range is 19 to 25, and the ideal is 22 to 24. McCain scores. Effect: Half a year younger.

Blood Pressure: At 134 over 84, McCain's blood pressure is not optimal. The American Heart Association advises maintaining a blood pressure below 120 over 80, but Roizen says the ideal is 115 over 75. Keeping blood pressure down is important, because hypertension is the leading reason arteries age, setting the stage for heart attacks, strokes, memory loss, wrinkling of the skin and impotence. McCain's blood pressure is well above the ideal. That said, he has lower blood pressure than most 71-year-olds, who average 145 over 89. Effect: nine-tenths of a year younger.

Cholesterol : Taking cholesterol-lowering drugs, McCain has brought his total cholesterol down to 192. That's below the 200 threshold that starts to worry doctors. His ratio of LDL (bad cholesterol) to HDL (good cholesterol) is fair, with his LDL at 123 and HDL at 42. But his triglycerides are elevated, at 135. Triglycerides are an independent risk factor for arterial aging, wiping out some of the advantage McCain earned for bringing down his total cholesterol. Effect: 1.2 years younger.

Stress Test: McCain's doctor noted that the candidate lasted 10 minutes during a recent cardiovascular stress test. Many younger men last only five or six minutes. Roizen estimates that 10 minutes would give McCain a metabolic equivalent score—a measure of how hard you're working when you exercise compared with resting metabolic rate—of 8.5, considered quite vigorous. Effect: 3 years younger.

Family Longevity: McCain's father died at 70 of cardiac-related problems. But his mother, 96, is still famously campaigning with her son. That shows a good genetic endowment. Effect: 1.5 years younger.

Cancer History: McCain has had four cancerous lesions removed from his skin. Of these, the most serious was the malignant melanoma he suffered in 2000. It was considered "intermediate risk" because of its thickness, but lymph nodes removed at the time showed no sign that the cancer had spread. The fact that he's survived more than five years is a good sign, so his cancer history doesn't add to his Real Age. Effect: 0.